From: Dan Schatzberg <schatzberg.dan@gmail.com>
To: Hillf Danton <hdanton@sina.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH 1/3] loop: Use worker per cgroup instead of kworker
Date: Tue, 6 Apr 2021 14:59:57 -0400 [thread overview]
Message-ID: <YGyvra69F/DIa7KI@dschatzberg-fedora-PC0Y6AEN.dhcp.thefacebook.com> (raw)
In-Reply-To: <20210403020902.1384-1-hdanton@sina.com>
Hi Hillf, thanks for the review
On Sat, Apr 03, 2021 at 10:09:02AM +0800, Hillf Danton wrote:
> On Fri, 2 Apr 2021 12:16:32 Dan Schatzberg wrote:
> > +queue_work:
> > + if (worker) {
> > + /*
> > + * We need to remove from the idle list here while
> > + * holding the lock so that the idle timer doesn't
> > + * free the worker
> > + */
> > + if (!list_empty(&worker->idle_list))
> > + list_del_init(&worker->idle_list);
>
> Nit, only queue work if the worker is inactive - otherwise it is taking
> care of the cmd_list.
By worker is inactive, you mean worker is on the idle_list? Yes, I
think you're right that queue_work() is unnecessary in that case since
each worker checks empty cmd_list then adds itself to idle_list under
the lock.
>
> > + work = &worker->work;
> > + cmd_list = &worker->cmd_list;
> > + } else {
> > + work = &lo->rootcg_work;
> > + cmd_list = &lo->rootcg_cmd_list;
> > + }
> > + list_add_tail(&cmd->list_entry, cmd_list);
> > + queue_work(lo->workqueue, work);
> > + spin_unlock_irq(&lo->lo_work_lock);
> > }
> [...]
> > + /*
> > + * We only add to the idle list if there are no pending cmds
> > + * *and* the worker will not run again which ensures that it
> > + * is safe to free any worker on the idle list
> > + */
> > + if (worker && !work_pending(&worker->work)) {
>
> The empty cmd_list is a good enough reason for worker to become idle.
This is only true with the above change to avoid a gratuitous
queue_work(), right? Otherwise we run the risk of freeing a worker
concurrently with loop_process_work() being invoked.
next prev parent reply other threads:[~2021-04-06 19:00 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-02 19:16 [PATCH V12 0/3] Charge loop device i/o to issuing cgroup Dan Schatzberg
2021-04-02 19:16 ` [PATCH 1/3] loop: Use worker per cgroup instead of kworker Dan Schatzberg
2021-04-06 1:44 ` Ming Lei
2021-04-02 19:16 ` [PATCH 2/3] mm: Charge active memcg when no mm is set Dan Schatzberg
2021-04-03 5:47 ` [External] " Muchun Song
2021-04-02 19:16 ` [PATCH 3/3] loop: Charge i/o to mem and blk cg Dan Schatzberg
2021-04-06 3:23 ` Ming Lei
[not found] ` <20210403020902.1384-1-hdanton@sina.com>
2021-04-06 18:59 ` Dan Schatzberg [this message]
[not found] ` <20210407065300.1478-1-hdanton@sina.com>
2021-04-07 14:43 ` [PATCH 1/3] loop: Use worker per cgroup instead of kworker Dan Schatzberg
2021-04-12 15:45 ` [PATCH V12 0/3] Charge loop device i/o to issuing cgroup Johannes Weiner
2021-04-12 15:50 ` Jens Axboe
-- strict thread matches above, loose matches on Subject: below --
2021-06-10 17:39 [PATCH V14 " Dan Schatzberg
2021-06-10 17:39 ` [PATCH 1/3] loop: Use worker per cgroup instead of kworker Dan Schatzberg
2021-06-03 14:57 [PATCH V13 0/3] Charge loop device i/o to issuing cgroup Dan Schatzberg
2021-06-03 14:57 ` [PATCH 1/3] loop: Use worker per cgroup instead of kworker Dan Schatzberg
2021-03-29 14:48 [PATCH V11 0/3] Charge loop device i/o to issuing cgroup Dan Schatzberg
2021-03-29 14:48 ` [PATCH 1/3] loop: Use worker per cgroup instead of kworker Dan Schatzberg
2021-03-16 15:36 [PATCH v10 0/3] Charge loop device i/o to issuing cgroup Dan Schatzberg
2021-03-16 15:36 ` [PATCH 1/3] loop: Use worker per cgroup instead of kworker Dan Schatzberg
2020-08-31 15:36 [PATCH v8 0/3] Charge loop device i/o to issuing cgroup Dan Schatzberg
2020-08-31 15:36 ` [PATCH 1/3] loop: Use worker per cgroup instead of kworker Dan Schatzberg
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